But according to the U.S. Environmental Protection Agency (EPA), passenger vehicle classification is determined by other criteria. If that sum is at least 100 cubic feet but less than 110 cubic feet, the vehicle is considered a compact car. Compact cars offer some advantages over larger vehicles, including the fact that they tend to be less expensive, depending on the make and model. Some compact cars also rank as some of the most fuel-efficient cars you can buy, though that will vary by the make and model. It's not all good, though; compact cars will come with tradeoffs, including less interior volume than larger vehicles and possibly reduced engine power than larger vehicles as well, due to smaller engines.